The Mariners have acquired right-handed reliever David Phelps from the Marlins in exchange for a package of four prospects. 

Phelps, 30, has pitched to a 3.45 ERA and 2.43 K/BB ratio in 47 innings this season. Last season, he was even better as a high-volume reliever for the Marlins. Phelps is owed the balance of a $4.6 million salary for 2017, and he's not eligible for free agency until after the 2018 season. 

On Seattle's side of things, the move signals that they'll indeed stay the course when it comes to trying to contend in 2017. GM Jerry Dipoto is limited by his sub-par farm system when it comes to acquiring impact talents in trade, which is why this Phelps deal might be the biggest splash the M's make leading up to the July 31 non-waiver deadline. 

As for the Marlins, they're getting outfield prospect Brayan Hernandez as the headliner. Hernandez, 19, was signed as an amateur free agent out of Venezuela. Across parts of three minor-league seasons, he's batted .257/.312/.390 with 35 stolen bases in 144 games. The other three prospects, per Joel Sherman, are right-hander Brandon Miller (age 22, 3.32 ERA in 31 minor-league starts, reached Midwest League), right-hander Pablo Lopez (age 21, 4.06 ERA in 60 games/46 starts, reached California League), and right-hander Lukas Schiraldi (age 23, 4.65 ERA in 97 games/48 starts, reached California League). Per MLB.com, Hernandez, Miller, and Lopez rank sixth, 16th, and 22nd, respectively, on the Mariners' top prospects list.